A cylindrical bearing member has been used as a slide bearing such as a bearing body for a rotating shaft or a bushing for a chain by inserting a shaft, a pin and the like into a pipe-shaped member.
In such a cylindrical bearing member, there have been formed a number of bottomed or blind grooves, serving as oil reservoirs for a lubricating oil. The grooves are parallel to the axial direction on an inner circumferential surface of the cylindrical bearing member for improving the lubricity between the inner circumferential surface for the bearing surface and the shaft, pin or the like.
Namely, the conventional blind groove for an oil reservoir in a cylindrical bearing member has been manufactured by subjecting a pipe-shaped seamless cylindrical blank formed by forging or the like or by milling such as undercutting, broaching or the like, or has been manufactured by forming a blind groove for an oil reservoir on a surface of a thin rectangular basic material such as a band steel, a flat band or the like by pressing, machining or rolling, then forming the rectangular basic material into a cylindrically formed product (cylindrical member) so that the both side edges of the basic material are opposed to each other, and inserting a core punch into the cylindrically formed product to push this product into a circular opening die (see Japanese Patent No. 2,963,652).